Spark-plug.



H. F. PROVANDB.

SPARK PLUGE APPLICATION ULEB MAY 24.1909.

Patented Apr. 12, 1910.

narra AtieneLiss earns r o sito,

HERBERT E'. PROVJLVDIIT,` OF BOSTON, MASSACHUSETTS, ASSIGNOR OF ONE-HALF T0 THE RANDALL-FAICHNEY COMPANY, OF BOSTON, MASSACHUSETTS, A GQRPQRA TION OF MASSACHUSETTS.

SPARK-PLUG. f

' Specification of Letters Patent.

Application filed May 24, 1909.

Patented Apr., i2, Q. sei-iai 110.497,86.

To all whom it 'may concern:

Be it kn Wn that I, HERBERT F. PRovAN- Din, ot Boston, in the county of Suffolk and State ot' Massachusetts, have invented certain new and useful Improvements in Spark-Plugs, ot which the following is a specification.

This invention relates to a spark plug intended for use in an internal combustion engine as an igniter, and it has for its object to provide a plug of this character of such construction that the stein Ywhich passes through the longitudinal center ot' the plug and supports one of the spark points or electrodes, constitutes also a sight opening substantially in alincincnt with the sp'ark gap between the two opposed spark points, so that an observer may determine the condition of the interior of the cylinder and ascertain Whether the spark plug is operating properly or not, Without removing the plug troni the cylinder or combustion chainber, an unobstructal view ot the spark gap through the longitudinal center otthe spark plug being provided.

The invention consists in the improvements which l Will non proceed to describe and claim.

Ot the accompanying drawings, forming a part ot this specificatiora-Figure 1 represents a longitudinal section ot a spark plug embodying nl xf invention. Fig. 2 represents a section on line ot Fig. l.

The saine reference characters indicate the saine parts in both figures.

ln the drawings,-12 represents a casing or bushing adapted to be detachably secured to the explosion chamber or cylinder ot' an internal combustion engine, the casing being here shown as provided with an external screw thread 1,3 adapted to engage an int-ernal thread in the wall ot such chamber.

1l represents a plug or body otl suitable insulating material, Isuch as porcelain, which is insertiblc in the casing 1Q., and as here shown. has an' eiilargclnent 15.y one end ot which abuts against an internal shoulder 1G in the casing.

17 represents a gland, the externally threaded portion ot which engages an internal screw thread 1S in theI casing 12, the diameter of the portion of the casing containing the screw thread 18 being greater than that of the shoulder 16. The inner end ot the gland is therefore adapted to bear on the outer end of the enlargement 15, so that the plug 14 is securely clamped between the said shoulder and gland. The'plug 111 is tubular, a longitudinal orifice or bore 19 being formed through it from end to end,

said bore being enlarged at the inner end of the plug to form a shoulder 20.

21 represents a tubular. metallic steln which is formed to enter and closely fit the bore of the plug ,1+i and extend through the saine, the ends ot' the stern projecting from opposite ends of the plug.A rlhe projecting inner end of the plug is provided With an electrode or spark point Z2 which is adapted t?) ccperate in the usual Way With a corresponding electrode or spark point Q3 alixed to the casing 12, 'the opposed ends ot'said spark point being separated by a spark gap 24, as usual. The stern 21 is provided ivith an enlargement 25 which is seated on the shoulder 20 of the plug 111-. The projecting outer end of the stem 21 is screw threaded, and provided with a nut 2G which bears on the outer end of the plug 111, and secures the stem 21 and spark point 22 in place.

It Will be seen that the bore 27 of the tubular stern 21 constitutes a sight opening eX- tending through. the longitudinal center of the spark plug, substantially in alineinent 'with the spark gap 24, so that an observer inay readily determine Whether sparks are properly passing across the spark gap, and Whether the explosions are properly occurring Within the chamber'. To prevent the escape ot' gases through the sight opening, I provide a plate. 29, which may be ot any suitable translucent or transparent material, such as inica or glass, this plate being held across the outer end of the tubular stein 21 by suitable ineans such as acollar il() Which is -internally threaded t-o engage an external thread formed on the nut 2G, the collar 30 being provided With a shoulder 21 between which and the outer end of the nut 26 the plate 29 is clamped The collar has an orifice 3Q Which const-itutes a continuation off-the above mentioned sight opening. through which the oritice 39. extends is preferably reduced and externally threaded to form a shank 3S adapted to engage a binding nut Se Which secures an electric conductor to the collarO. I

I do not limit myself to the details oiA constructionlhere shown and described, and

The portion of t-he collar i my the same may be modified in various particulars without departing from the spiritpof my invention, which is embodied in a spark plug 'having an insulating body, spark points, and a tubular metallic stem'extending through the insulating body, and supporting one of said points, said stem having a sight opening extending through the plug 'substantially 'in alineinentvvith the spark gap between the spark points.

The terms longitudinal center and alinement are used relatively, and I do not wish to be understood as limiting myself to the location-of the sight opening at the exactlongitudinal center ofthe plug, or in exact alinenient With the spark gap, it being obvious that any location of the sight opening Within the periphery of the insulating plug whichv Will enable the light,

emitted by the spark to be seen through the sight opening, will be in accordance With. invention'. Heretofore, an annular space has been provided between the' casing l2 and the insulating plug 14this space constituting a sight opening which is provided with a light-transmitting partition 'of translucent material. formed as an annu- A y lar flange projecting from the periphery of ythe insulating plug, and extending across said space, the flange being engaged with. clampingmembers on the casing. By arranging .the sight opening entirely within the periphery ofthe insulating plug, I enable the body of the plugto be directly engaged With the casing, instead of relying on a translucent' flange attached to' the body of the plug and projecting outwardly there- The plate29,lwhich -inay be termed also .a light-transmitting artition or'a lens, is preferably a cylindrical body of glass or other suitable light-transmitting *material 'inclosed in a bushing 36, which may be a tube of copper, the ends of which are spun over the. ends of the lens 29, thus forming flanges or gaskets 37 which are in contact 1 with the nuts 26 and the shoulder 31 and cooperate with said parts in forming gastight joints.v

The collar 30 and the lens are removable `from the insulating plug M to permit the insertion of a slender cleaning device, suoli as is commonly used for cleaning pipestems, the said device being insertible in the sight opening and adapted to be passed through -the same to clean the sparking' points, the location of the sight opening inA substantial alineinent with the spark points ,enablingA the cleaning device to act etleetively on the'spark peints, so that the -latter may be cleaned without rcmovingthe plug from the cylinder? Gaskets or washers 38 of asbestos or other eompressible refractory material are preferably interposed between the ends of the enlargement 15 of the insulating plug and the parts of the casing Which coperate'with. said enlargement in securing the plug to the casing.- Similar gaskets 39 may be interposed between the enlargement 25 of the stem 21vand the shoulder 20, and

also between theouter' end of theinsulating plug and the-faces `of the nut 2.6 and collar' 30, which oppose said outer end.

claim: A vl. A spark plug having an insulating body, spark points, a metallic steinsupportingone of the spark points and having a sight opening extending longitudinally through the body of the plug, a light-transmitting partition which prevents the passage of gases through the opening, and means for detachably securing said partition to the plug.

2. A- spark plug having an insulating body, spark points, a tubular metallic stem extending through the insulating body of the plug, the bore of the' stein eonstitutinga sight opening, a nut engaged with the outereiid of the stein and'bearing on vthe outer end of the insulating body of the plug, said nut being externally threaded, an internally threaded collar engaged with said nut and provided with an .externally threaded stem and with an orifice extending through the Astem and constituting an extension of the sight oaenin'o. and a binding nut enga ed :p v c, n a, i with said stem.

3. AV spark plug comprising a casing ha'vving a spark point, aA tubular insulating plug secured in the casing, a tubular metallic stem extending through the plug and supporting another lspark point, vthe bore of said stem constituting a sight opening in substantialA aliueuurnt with the spark gap between the spark points, a 'leusirxteni'ling agross the outer end of the stem, and means for detachably securing the lens in its operative position.

ing a sparkpoint, a tubular insulating plug secured in the easing, a tubular metallic stein extending through the plug and supportinganoher spark point, the bore of saidv stein constituting a sight opening, in substantial alinenieut with the spark gap between the spark points, a lensextcnding across the.

signature, in presence of two wtnesios.

llliltllllt'l l". PR( )VANHE ii'ti'xesses:

(l. F, noww,

4. A spark plug comprising a casing hav- 

